Blood transfusions are life-saving procedures used in medical conditions and emergencies to replace lost components of the blood. According to the American Red Cross, someone in the U.S. needs blood every two seconds, more than 44,000 blood donations are needed every day, and a total of 30 million blood components are transfused each year in the U.S. A single car accident victim can require as many as 100 pints of blood. In addition, patients with diseases such as sickle cell anemia and cancer affect millions of people in the U.S., and patients with these diseases can require frequent blood transfusions throughout their lives. Major worldwide blood shortages, infected donated blood, the necessity for blood typing, a short shelf life of stored blood, and the inadequacy of stored blood for use in certain situations such as battlefield scenarios and trauma, have led scientists to synthesize and test blood substitute products. Although non-blood volume expanders for cases where only volume restoration is required are widely available, to date there is no well accepted oxygen-carrying blood substitutes. Perfluorocarbon based oxygen-carrying products rely on dissolved oxygen, dissolve 3 times more in oxygen than red blood cells, and have a long shelf life. However, PFC-based products have failed due to poor oxygen delivery functionality, short half-life in circulation, complement activation by pluronic surfactants in PFC-based products, and require cold storage at freezing temperatures. On the other hand, currently available hemoglobin based oxygen carriers (HBOCs) have a short period of functionality during circulation, have poor oxygen capture and release dynamics, and are incompatible with dry storage, limiting their use in remote areas. In addition, hemoglobin based oxygen carriers have been shown to be unsafe, causing hemodynamic and gastrointestinal perturbations related to nitric oxide (NO) scavenging, free radical induction, and alteration of biochemical and hematological parameters such as increased liver enzyme levels and platelet aggregation.
Therefore, there is a need for a safe and efficient oxygen-carrying blood substitute having adequate oxygen capture and release dynamics that does not interfere with normal regulation of blood vessel caliber, is capable of maintaining oxygen-carrying functionality during circulation, and is amenable to extended storage and ease of use.